1. Field of the Invention
The present invention related to a latching or fastening mechanism for an access lid to a subsurface chamber for servicing aircraft.
2. Description of the Prior Art
At modern aircraft terminals the servicing of aircraft on the ground is frequently performed using subsurface pits, which are often prefabricated structures. Such aircraft servicing pits are installed at aircraft docking, fueling, and loading areas beneath the surface of the tarmac across which aircraft travel during docking and departure maneuvers. The pits form a subsurface chamber and are typically constructed of fiberglass, steel, concrete, or aluminum. These pits are often constructed as complete enclosures with surrounding walls, a floor, and an access lid at the top seated within a frame disposed about the neck of the prefabricated pit. When the lid is closed it lies substantially flush with the surface of the tarmac. Such pits are installed below the surface of loading and refueling aprons at aircraft terminals, remote parking locations, and aircraft maintenance bases.
The purpose of the pits is to allow ground support functions to be carried out from subsurface enclosures. These ground support functions include the provision of fuel, the provision of electricity to an aircraft while it is in the docking area, the provision of air for cooling the aircraft interior, the provision of pressurized air for starting the aircraft engines, and for other aircraft support activities on the ground. The use of subsurface pits eliminates the need for mobile trucks, carts, and other vehicles which are otherwise present in the loading area and which interfere with the arrival and departure of aircraft in the vicinity of a loading gate.
The use of subsurface pits also allows the provision of fuel, power, cooling and pressurized air, and other supplies from a central location. The necessary fluid supplies and electrical power can be generated or stored with a greater efficiency at a central location, as contrasted with mobile generating or supply vehicles.
The pits located below the aircraft terminal area house valves, junction boxes, cooling air terminations, and other terminal equipment that is temporarily connected to an aircraft that has been docked. Umbilical pipes and lines, otherwise housed within the pits, are withdrawn from them through hatches therein and are coupled to a docked aircraft to supply it with fuel, air for cooling the aircraft interior, pressurized air for starting the engines, and electrical power.
The pits are constructed with either hinged or totally removable lids that can be moved between open positions allowing access to the pits and closed positions which are flush with the surfaces of the docking, loading, or refueling areas across which aircraft travel and beneath which the pits are mounted. To ensure that the pit lids remain flush with the surrounding surfaces, it is desirable to employ a latching mechanism. Very typically such a latching mechanism involves a catch depending from the underside of the edge of the pit lid remote from the hinge about which the pit lid is rotatably mounted to its surrounding frame. The catch engages a latch bar secured to the interior wall of the pit. The catch is normally moved in rotation about a horizontal axis by means of a lever arm located in a cavity at the underside of the pit lid remote from the axis at which the pit lid is mounted to the frame. Access to this cavity to operate the latch mechanism is normally provided by a gap between the frame and the pit lid adjacent to the lever arm.
To open the pit lid the user inserts the fingers of one hand into the gap and beneath the lever arm at the underside of the pit lid. The user then presses upwardly on the lever arm, thereby rotating it. The lever arm and catch mechanism operate in the manner of a bell crank, so that rotation of the latching mechanism lever arm pulls the catch from beneath the latch bar and allows the user to open the pit lid. One prior mechanism of this type is described in U.S. Pat. No. 4,739,896, which is hereby incorporated by reference in its entirety.
One difficulty with conventional latch mechanisms of this type that has persisted throughout the years is that the gap that provides access to the pit latch lever arm and the cavity in which the lever arm is mounted often becomes clogged with dirt and debris so that the user must first clean out these areas in order to free the pit lid latch lever arm so that it may be moved. Since the gap at the edge of the pit lid is located below grade and the cavity in which the pit latch lever arm is located lies underneath the edge of the pit lid, it is often quite difficult to clean out the dirt and other loading apron and runway debris that collects in order to free the lever arm of the latch mechanism.
The present invention provides a unique latching mechanism for an aircraft service pit lid that overcomes the difficulties of the prior art devices described. More specifically, the aircraft service pit latch mechanism of the present invention provides an actuating rod that acts through the structure of the pit lid, rather than externally at the pit lid edge. Moreover, the unique latching structure of the present invention allows the cavity in which the latch actuating lever is seated to be located at the upper surface of the pit lid, rather than at the undersurface of the lid. Nevertheless, the latch lever arm is constructed in such a manner that its seats snugly within an upwardly facing recess on the top of the pit lid. As a consequence, there is relatively little space within which dirt can collect and it is much easier to clean any dirt and debris from around the edges of the latch handle seated in the lever arm seating recess, since there is easy access to this area.
In one broad aspect the present invention may be considered to be an aircraft servicing pit latch mechanism for holding and releasing a pit lid mounted in a frame atop a subsurface aircraft servicing pit. The pit lid has an upper surface and also an undersurface. The latch mechanism of the invention is comprised of a latch or operating lever storage recess defined in the upper surface of the pit lid, an actuator rod passageway formed in the pit lid and extending between the latch operating lever storage recess and the underside of the pit lid, a catch located in alignment with the actuator rod passageway at the undersurface of the pit lid and mounted for rotation about a horizontal axis of catch rotation, an actuator rod disposed for reciprocal movement in the actuator rod passageway, and a latch operating lever. The latch operating lever has opposing latch handle and actuator rod operating ends. The latch handle is mounted between its opposing ends to the pit lid at a fulcrum about a horizontal latch operating lever axis of rotation. The latch operating lever is thereby mounted for movement between a stored position residing within the lateral confines of the latch operating lever storage recess and an actuator rod engaging position. When the latch operating lever is in the actuator rod engaging position the latch handle end is raised out of the latch operating lever storage recess while the actuator rod operates and depresses the actuator rod to disengage the catch.
The actuator rod has opposing upper and lower ends. The pit latch mechanism of the invention is preferably further comprised of a of pair rollers, one located at each of the upper and lower ends of the actuator rod. The roller at the lower end of the actuator rod is mounted thereto on a lower roller axle oriented parallel to the axis of catch rotation. The roller at the upper end of the actuator rod is mounted thereto on an upper roller axle oriented parallel to the latch operating lever axis of rotation. The rollers are preferably comprised of roller bearings.
In a preferred embodiment of the invention the upper and lower axes of roller rotation are angularly displaced from each other by ninety degrees considered in a horizontal plane. Consequently, it is advisable to provide a longitudinal guideway in the actuator rod and a guide secured to the pit lid and projecting into the guideway to limit and restrict the actuator rod from rotation within the actuator rod passageway. This guide system ensures that the axis of rotation of the lower roller remains parallel to the axis of rotation of the catch and that the axis of rotation of the upper roller remains parallel to the axis of rotation of the latch operating lever.
Preferably the latch operating lever is an L-shaped structure and is provided with a handgrip at its latch handle end oriented at right angles relative to the pivoted portion of the latch operating lever. The latch handgrip that projects laterally from the latch handle end of the operating lever also resides within the lateral confines of the latch operating lever storage recess when the latch handle is in its stored position.
While the catch may be of the gravity operated type as described in prior U.S. Pat. No. 4,739,896, a spring is preferably provided on the underside of the pit lid to bias the catch toward and engaged position. Such a spring may be located within a shallow cavity in the underside of the pit lid above a portion of the catch located on the opposite side of the axis of catch rotation from the point of contact with the lower roller at the lower end of the actuator rod.
Preferably also the rod operating end of the actuator rod meets the structure of the pit lid to restrict rotation of the latch operating lever to an angle of less than ninety degrees. This ensures that when latch operating lever handle is released when the pit lid is lowered to its closed, horizontal position, the latch operating lever and its handle will drop back into the latch operating lever storage recess due to the force of gravity.
In another aspect the invention may be considered to be a latching mechanism for releaseably securing a pit lid having an upper surface and an undersurface and seated in a pit lid frame of a pit buried beneath a surface across which aircraft travel. The latching mechanism of the invention is comprised of a catch, a latch operating lever storage recess, an actuator rod passageway defined through the pit lid, an actuator rod mounted for reciprocal movement within the actuator rod passageway, and a latch operating lever. The catch depends from the undersurface of the pit lid and is mounted for rotational movement about a horizontal catch axis of rotation relative to the pit lid.
The catch may be moved between engaged and disengaged positions. The latch operating lever storage recess is formed in the upper surface of the pit lid vertically above the catch. The actuator rod passageway that is defined through the pit lid leads between the latch operating lever storage recess and the undersurface of the pit lid. The actuator rod is depressible to bear against the catch to disengage it from the pit. The latch operating lever has opposing handle and actuator rod operating ends. The latch operating lever is hinged to the pit lid between its opposing ends and is rotatable about a horizontal fulcrum. The latch operating lever may be rotated between a stored position residing within the lateral confines of the latch operating lever storage recess and a raised position in which the handle end is lifted out of the latch operating lever storage recess and in which the actuator rod operating end depresses the actuator rod into the actuator rod passageway.
In still another aspect the invention may be considered to be an improvement to a subsurface pit for use below a surface across which aircraft travel on the ground. Such a pit has a pit lid frame and the pit lid with an upper surface and an undersurface. The pit lid is set in the frame and can be lifted relative to the frame. A pivoted catch is located beneath the pit lid at the undersurface thereof. The catch is engageable with the pit to hold the pit lid seated in the frame. According to the improvement of the invention a latch operating lever storage recess is defined in the upper surface of the pit lid above the pivoted catch. An actuator rod passageway is defined through the pit lid and terminates in an upper opening in the latch operating lever storage recess and in a lower opening at the undersurface of the pit lid in registration with pivoted catch. An actuator rod is disposed in the actuator rod passageway for reciprocal movement therewithin. The actuator rod is depressible downwardly to bear against the pivoted catch to disengage the pivoted catch relative to the pit. The latch operating lever has opposing latch handle and reciprocating rod operating ends and is pivotally mounted between those ends to the pit lid proximate the upper surface thereof. The latch operating lever is rotatable between a catch engaging position lying completely within the lateral confines of the latch operating lever storage recess and a raised position in which the latch operating lever depresses the actuator rod downwardly to disengage the catch.
The invention may be described with greater clarity and particularity by reference to the accompanying drawings.